Control device and method for operating a refrigerant compressor

ABSTRACT

Electronic control device for a refrigerant compressor, comprising at least one drive unit and a compression mechanism which is in operative connection with the drive unit and has at least one piston which, in an operating state of the refrigerant compressor, moves back and forth in a cylinder of a cylinder block of the refrigerant compressor for the operational compression of refrigerant and is driven by a crankshaft of the drive unit, wherein the electronic control device of the refrigerant compressor is at least designed to detect at least one physical process parameter, preferably the rotational speed (n) of the crankshaft or the power consumption of the refrigerant compressor, and to detect a switch-off signal directed at the refrigerant compressor, said switch-off signal terminating a refrigerant compressor operating phase in which the refrigerant compressor is operated as intended with a positive operating torque; and is also designed to regulate a torque applied by the drive unit to the crankshaft so as to adjust the rotational speed (n) of the crankshaft, wherein the electronic control device is further designed to apply a braking torque to the crankshaft immediately after detecting the switch-off signal, wherein the braking torque is applied in the opposite direction to the positive torque acting during the operating phase and the value of this braking torque is a function of the detected physical process parameter, preferably the rotational speed (n) of the crankshaft or the power consumption of the refrigerant compressor.

FIELD OF THE INVENTION

This invention concerns an electronic control device for a refrigerant compressor, which comprises at least one drive unit and a compression mechanism that is in operative connection with the drive unit and has at least one piston that, in an operating state of the refrigerant compressor, moves back and forth in a cylinder of a cylinder block of the refrigerant compressor and is driven by a crankshaft of the drive unit for operational compression of refrigerant, where the electronic control device of the refrigerant compressor at least is designed to detect at least one physical process parameter, preferably the rotary speed of the crankshaft or the power consumption of the refrigerant compressor, to detect a shutoff signal directed to the refrigerant compressor, said shutoff signal ending an operating phase of the refrigerant compressor, in which operating phase the refrigerant compressor is operated, as designed, with a positive operating torque, and the electronic control device is configured to regulate a torque applied by the drive unit to the crankshaft for setting its rotary speed.

Furthermore, said invention concerns a refrigerant compressor for use in a refrigeration unit, preferably in a refrigerator or freezer, where the refrigerant compressor comprises an electronic control device according to the invention.

In addition, this invention concerns a refrigeration unit, preferably a refrigerator or freezer, with a refrigerant compressor according to the invention.

This invention further concerns a method for operating a refrigerant compressor that is suitable for use in a refrigeration unit, preferably in a refrigerator or freezer, which comprises a compression mechanism for compression of refrigerant and a drive unit, where the compression mechanism is driven by means of a drive shaft of the drive unit to which a torque is applied.

PRIOR ART

Electronic control devices of this kind are used in rotary speed-variable refrigerant compressors. Rotary speed-variable refrigerant compressors have the advantage that they can be matched more specifically to the refrigeration requirements of the object to be cooled; for example, they can be operated at a lower speed in the case of lower refrigeration requirements and at a correspondingly higher speed in the case of a higher refrigeration requirement.

The structure of refrigerant compressors has long been known. They essentially consist of a drive unit and a compression mechanism in the form of a piston that moves back and forth in a cylinder housing between a first and a second dead point, the piston being connected via a connecting rod to a crankshaft, which in turn is rigidly coupled to a rotor of the drive unit.

A brushless DC motor is typically used as the drive unit. In this case it is possible to determine the relative position of the rotor of the DC motor and thus the rotary speed of the motor or the compression mechanism on the basis of the emf induced in the motor winding (induced emf).

This method manages without separate sensors and therefore is especially easy to implement and is less susceptible to failure.

Noise problems arise in the case of refrigerant compressors according to the prior art, in particular during the stopping process, which immediately follows a phase in which the refrigerant compressor was operated with a positive operating torque as designed. Different gas forces (caused by the refrigerant pressure relationships in the system) and friction forces (the two together are called the load torque) act on the compression mechanism in the intake and compression phase, which, in a closer analysis, results in a rotary velocity of the crankshaft that varies widely and unevenly over the crank angle. In this patent application a basic distinction is made between the terms rotary velocity and rotary speed. The term rotary velocity is used when the actual, instantaneous angular velocity of the crankshaft is meant, whereas the term rotary speed is used when the average number of revolutions of the crankshaft per minute is meant, thus the value that is usually meant when speaking of the rotary speed of a refrigerant compressor.

Specifically, during the compression phase a load torque that is higher than in the intake phase acts on the compression mechanism and must be overcome by the operating torque of the drive unit in order to keep the compression process going. This increased load torque leads to a reduction of the rotary velocity of the crankshaft during the compression phase.

On the other hand, during the intake phase the gas forces cause a lower load torque than in the compression phase. This leads to an increase of the rotary velocity of the crankshaft during the intake phase.

Overall, a load torque that varies over the entire crank angle thus acts on the compression mechanism and thus on the crankshaft, and the range of variation of the load torque is primarily dependent on the pressure ratio in the refrigerant circuit and leads to variously high angular accelerations and thus to a rotary velocity of the crankshaft that is uneven over the crank angle during a rotation of the crankshaft.

In order to compensate for oscillations and vibrations of the compression mechanism during operation, the entire drive unit is mounted in a housing via spring elements. The characteristic frequencies of this oscillation system are between 5 Hz and 16 Hz according to compressor type.

Thus, during the compression phase, in particular when the refrigerant compressor is operating at rotary speeds under a range between 1000 rpm and 700 rpm, the increased load torque, which repeats during each crankshaft revolution, leads to impacts on the compression mechanism, which press the compression mechanism along with the drive unit into the spring elements and deflects them, where the impact frequency lies in the range of the characteristic frequency of the oscillation system, so that the deflections of the spring elements become larger with each crankshaft revolution, so that the compression mechanism and/or the drive unit can strike the housing, due to which undesired noise can form. This situation is also a reason that in the normal regulated operating phase the known refrigerant compressors are not operated below a range between 1000 rpm and 700 rpm, thus not in the rotary speed range that is critical with respect to noise generation. However, the described undesired noise generation of a refrigerant compressor at low rotary speeds does not arise only in the normal regulated operation, but rather mainly also during the stopping process, where it is necessary to pass through said low rotary speeds. As a rule, the stopping process occurs as follows:

if, after a normal regulated operating phase of the refrigerant compressor in which the refrigerant compressor was operated as designed with a positive operating torque, the target temperature of the object to be cooled, for example a cooling compartment of a refrigerator, has been reached, the electronic control device, of the refrigerator sends a signal (shutoff signal) to the electronic control device of the refrigerant compressor, with which it is reported to the latter control device that cooling output is no longer necessary, since the target temperature has been reached. It is known from the prior art that the electronic control device of the refrigerant compressor thereupon shuts off the drive or the positive drive torque at which the refrigerant compressor was operated as designed during the regulated operating phase (shutoff time). The stopping process thus begins immediately after the detection of the shutoff signal with the deactivation of the positive drive torque.

The crankshaft of the compression mechanism also runs through complete revolutions each time after the shutoff time, beginning at the first dead point (crank angle 0°), where first an intake phase (more correctly: intake and reexpansion phase) is passed through, during which refrigerant is drawn into the cylinder. Said intake phase theoretically ends when the cylinder has reached the second dead point (crank angle 180°). After that the compression phase (more correctly: compression and ejection phase) begins, during which the refrigerant in the cylinder is compressed and is ejected from the cylinder. The compression phase theoretically ends when the piston again has reached the first dead point (crank angle 360°). In practice, however, the actual compression of the refrigerant does not begin until a crank angle of about 210° has been reached (depending on refrigerant compressor, pressure ratios, valve design, etc.), but at any rate after 180°, and the intake phase begins at, about 30°, at any rate, however, after the first dead point.

The shutoff of the drive unit of the refrigerant compressor at a shutoff time, which shutoff time in reality does not coincide with the detection of the shutoff signal by the electronic control device, but rather lags a little behind in time, initiates the stopping process and leads to the crankshaft being in an undriven state (without positive drive torque) and it continues to rotate merely because of its inertia, until it comes to a complete stop, i.e. its rotary speed is 0. Colloquially speaking, one could also say that the refrigerant compressor “shuts down”.

During the undriven state the crankshaft runs solely because of the kinetic energy that it has at the shutoff point and its inertia. It thus rotates, so to say, uncontrolled and its rotary speed behavior is dependent on the load torque acting on the compression mechanism. The load torque leads to a steady reduction of the rotary speed of the crankshaft of the undriven rotating refrigerant compressor, so that the kinetic energy of the crankshaft becomes increasingly less until it, depending on the pressure ratios in the refrigerant circuit, no longer is sufficient to overcome the load torque (limit rotary speed).

It should be kept in mind that with the drive unit switched off, unlike during the normal regulated operating phase, there is no positive operating torque that counteracts the load torque, in particular the elevated load torque in the compression phase, so that with the drive unit switched off the impacts that act on the compression mechanism due to the increased load torque in the compression phase are unchecked, so to say, and therefore the effects with respect to the deflection of the spring elements are even more serious than is the case in the normal regulated operating phase, where the positive operating torque counteracts the impacts and dampens them somewhat.

This in turn leads to the deflection of the spring elements being even greater at low rotary velocities during the stopping process than during the normal regulated operation of the refrigerant compressor at the same low rotary velocities and thus there is a higher probability of a contact between the compression mechanism/drive unit and the housing, whereby a higher noise generation is generally connected.

Furthermore, for the case that the piston is exactly in a compression phase, when the kinetic energy of the crankshaft is no longer sufficient to overcome the load torque, the piston of the compression mechanism can possibly be pushed back in the direction of the second dead point, so that the direction of rotation of the compression mechanism is thus reversed.

An additional stopping jolt acting on the compression mechanism leading to an additional deflection of the spring elements is connected with the reversal of the direction of rotation.

It is precisely in the stopping process, where, as described above, no positive operating torque counteracts the load torque and the increased load torque acting in the compression phase is already producing an impact-like stimulation of the oscillation system in the region of its characteristic frequency, that the stopping jolt contributes to deflection of the spring elements even more, because of the reversed direction of rotation, so that the probability that the compression mechanism/drive unit impacts against the housing wall is again increased and thus undesired noise generation arises.

Ending the undriven phase by applying a braking torque and thus avoiding at least a kickback of the refrigerant compressor and thus the stopping jolt is known from the prior art. In this case the idea is to actively brake the crankshaft, which is undriven after the shutoff time, if the rotary speed goes below a certain value, by applying a braking torque and bringing it to a stop. For this it is necessary to monitor the rotary speed of the undriven crankshaft continuously after the shutoff point and to actively brake the crankshaft at a defined rotary speed, which in any case must still be sufficiently high to be able to overcome the load torque in the meantime—thus it must lie above the limit rotary speed—by means of the braking torque that is applied to the crankshaft at the end of the stopping process.

For reasons of energy efficiency the braking torque that contributes to the stopping of the crankshaft can meaningfully first be applied after the crankshaft goes below a certain rotary speed, since the energy expenditure of a braking torque that causes a crankshaft rotating at a rotary speed higher than said specific speed to stop would be unreasonably high. To achieve said specific rotary speed, the prior art calls for letting a comparably long period of time pass before the said braking process, said time extending between the shutoff signal and the application of the braking torque and during which time the crankshaft runs without being subjected to a positive operating torque or a counteracting braking torque. The stopping process that is initiated at the shutoff time thus, in the case of electronic control devices according to the prior art, consists of the time in which the crankshaft runs uncontrolled and the final braking process, which is intended to bring about the stopping of the crankshaft.

However, it is problematic for the reasons discussed above that the stopping process becomes drastically lengthened, in particular due to allowing the crankshaft to run in order to achieve the specified rotary speed at which the braking torque can be meaningfully applied. In addition to the accompanying noise generation, which is caused by the—initially very slow—passage through the critical rotary speed range, there is the additional problem that the electronic control device must be supplied with power for purposes of continuous monitoring of the rotary speed, even during the entire time in which the crankshaft runs uncontrolled. A disconnection of the power supply of the electronic control device, which usually takes place via the electronics of the refrigeration unit in which the refrigerant compressor is used, thus cannot take place in the electronic control devices according to the prior art until the crankshaft has been brought to a stop.

To sum up, it can thus be established from these arguments that the operation of known rotary speed-variable refrigerant compressors at low rotary velocities gives rise to a stimulation of the oscillation system in the region of its characteristic frequencies and therefore leads to undesirable noise generation. Since this effect is observed especially strongly during the stopping process, in which the crankshaft of the refrigerant compressor must pass through a rotary speed range that is critical with respect to noise generation, basically a stopping process that is as short as possible is desirable. In the electronic control devices as are known from the prior art this desire is, however, opposed by the need to reduce the rotary speed of the crankshaft first below a certain value before the braking torque leading to the stopping of the crankshaft can be applied with reasonable expenditure of energy and without danger to any electronic components of the control device.

PROBLEM OF THE INVENTION

Therefore, it is a problem of this invention to make available an electronic control device for a refrigerant compressor that enables a rapid and energy-efficient stopping of the refrigerant compressor, in particular the crankshaft of the refrigerant compressor, and keeps a noise generation caused by operation of the refrigerant compressor at low rotary velocities—thus in particular during the stopping process—as low as possible.

Moreover, it is a problem of the invention to make available a refrigerant compressor and a refrigeration unit that offers the said advantages.

In addition, it is a problem of the invention to make available a method for operating a refrigerant compressor that enables a rapid and cost-efficient stopping of the refrigerant compressor and that keeps noise generation connected with braking and stopping as low as possible.

DESCRIPTION OF THE INVENTION

One of the said problems, in the case of an electronic control device according to the invention for a refrigerant compressor, which comprises at least

-   -   a drive unit and     -   a compression mechanism that, in an operating state of the         refrigerant compressor, is in operative connection with the         drive unit and has at least one piston that moves back and forth         in a cylinder of a cylinder block of the refrigerant compressor         for compression of refrigerant as designed and is driven via a         crankshaft of the drive unit,         where the electronic control device of the refrigerant         compressor is configured at least     -   to detect at least one physical process parameter, preferably         the rotary speed of the crankshaft or the power consumption of         the refrigerant compressor,     -   to detect a shutoff signal directed to the refrigerant         compressor, said shutoff signal ending an operating phase of the         refrigerant compressor, in which operating phase the refrigerant         compressor is operated as designed with a positive operating         torque,         and is configured     -   to regulate a torque applied by the drive unit to the crankshaft         to set its rotary speed, is solved in that the electronic         control device is additionally configured to apply a braking         torque to the crankshaft immediately after detecting the shutoff         signal, where the braking torque is directed opposite the         positive rotary torque that exists during the operating phase         and the value of said braking torque is a function of the         detected physical process parameter, preferably the rotary speed         of the crankshaft or the power consumption of the refrigerant         compressor.

The application of the braking torque to the crankshaft according to the invention leads to the braking process starting immediately after the operating phase, in which the refrigerant compressor was operated with a positive operating torque, and thus beginning at the same time as the stopping process. A lengthening of the stopping process known from the prior art by letting the crankshaft run in order to reduce its rotary speed before the actual braking process, which is initiated by application of the braking torque, is thus avoided. Instead, the braking process begins at the moment immediately following the detection of the shutoff signal and as a rule extends up to the stopping of the crankshaft. Thus, overall, the result is a stopping process that is clearly shorter than in the prior art, which is due to the avoiding of letting the crankshaft run on the one hand and quicker braking of the crankshaft by the braking process, which is initiated earlier, on the other.

Moreover, the choice of the value of the braking torque as a function of the detected process parameter of the refrigerant compressor enables, an especially energy-efficient braking of the crankshaft, since different braking torques can be applied to the crankshaft at different process time points during the braking process.

The choice of the braking torque as a function of the rotary speed of the crankshaft of the refrigerant compressor turned out to be especially advantageous, since high braking torques, in particular, at the beginning of the braking process—thus when the rotary speed is still high—go hand-in-hand with an elevated energy loss. Moreover, a rapid and at the same time energy-efficient slowing of the crankshaft can be accomplished by varying the braking torque that is applied in each case over the entire braking process in dependence on the relevant rotary speed of the crankshaft.

For this reason, in a preferred embodiment of the electronic control device according to the invention, it is provided that the physical process parameter is the rotary speed of the crankshaft.

Since an energetically favorable braking of the crankshaft can be achieved in particular at low rotary speeds, in another preferred embodiment of the electronic control device according to the invention it is provided that the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is inversely proportional to the rotary speed of the crankshaft that the crankshaft has at the moment of the detection of the shutoff signal.

Through this, the braking torque applied to the crankshaft at the beginning of the braking process—and thus immediately after detection of the shutoff signal—will be selected to be lower or higher in the case of higher or lower rotary speeds during the operating phase preceding the shutoff signal. At lower rotary speeds a corresponding choice of the braking torque will lead to a further shortening of the stopping process, since the crankshaft will already be subjected to a higher braking torque at the beginning of the stopping process. In the case of high rotary crankshaft speeds at the moment of the detection of the shutoff signal, the choice of the braking torque according to the invention will on the other hand lead to a lower energy demand over a wide extent of the stopping process, while the stopping process according to the invention will nevertheless be shortened by the braking torque that is already applied at the beginning of the stopping process, by comparison with stopping processes in accordance with the prior art that have a phase in which the crankshaft is allowed to run.

In order to reduce the length of the stopping process further and to keep the noise generation that accompanies the operation of the refrigerant compressor at low rotary velocities as low as possible, it is advantageous to maintain the braking torque applied at the beginning of the stopping process over the entire stopping process. For this reason, in another preferred embodiment of the electronic control device according to the invention, it is provided that the braking torque is maintained up to a complete stop of the crankshaft.

In an especially preferred embodiment of the electronic control device according to the invention, it is provided that the braking torque applied to the crankshaft develops a braking profile, where a function defining the course of the braking profile is stored by the electronic control device and preferably comprises a linear dependency on the current rotary speed of the crankshaft and/or the elapsed time since detection of the shutoff signal.

The realization of the braking torque as a braking profile, which represents the timewise course of the braking torque, enables an optimum matching of the value of the braking torque to the decreasing rotary speed of the crankshaft during the stopping process. Starting from the value of the braking torque at the beginning of the stopping process—and thus immediately after detection of the shutoff signal—it is, for example, possible to increase the value of the applied braking torque in the course of the stopping process in order to progressively increase the braking effect. This can take place in dependence on the actual rotary speed of the crankshaft, which itself in turn is dependent on the applied braking torque and decreases further with continuing duration of the stopping process. Alternatively, a measurement and/or evaluation of the current rotary speed in each case during the stopping process can be omitted and the previously established braking profile can be determined as a function of the time elapsed since detection of the shutoff signal.

In both cases it is necessary that a function defining the specific braking profile—with the function parameters current rotary speed of the crankshaft and/or time elapsed since detection of the shutoff signal—be stored by the electronic control device. Overall in this way an especially advantageous braking profile can be selected, which leads to the crankshaft being only lightly braked at the beginning of the stopping process and the braking effect becoming increasingly greater with continuing reduction of the rotary speed. Through this, the duration of the stopping process and the energy consumption of the refrigerant compressor during the stopping process can be reduced.

In another preferred embodiment of the electronic control device according to the invention, it is provided that the electronic control device is configured to compare the rotary speed of the crankshaft, preferably a number of times, especially preferably continuously, with preset rotary speed values in a braking time period extending between the detection of the shutoff signal and the complete stop of the crankshaft.

In this way it becomes always possible to establish the rotary speed regime, of a plurality of such speed regimes established by the specific choice of the preset rotary speed values, in which the crankshaft is running during the braking time period. In this connection it turned out to be particularly advantageous to compare the current rotary speed with the preset rotary speed values a number of times, or as often as technically possible, thus continuously, during the braking time.

It is provided according to the invention that the function defining the braking profile that is stored by the electronic control device establishes a different value or a different course (for example, slope, curve) of the applied braking profile for each rotary speed regime, thus for all values of the current rotary speed of the crankshaft lying between two of the preset rotary speed values.

Thus, in an especially preferred embodiment of the electronic control device according to the invention, it is provided that the course of the braking profile essentially follows a piecewise linear function, where a segment of the braking time is associated with each of the preset rotary speed values, within which said piecewise linear function exhibits an essentially constant slope.

This enables the electronic control device according to the invention to divide the braking time into any number of segments, where the braking profile in each of said segments follows the course of a linear function with a specific slope associated with the relevant region. In this way the braking profile can be applied to the crankshaft in an especially simple, stable and easily implemented way and at the same time an optimum adjustment of the relevant braking torque to the instantaneous speed of the crankshaft can be ensured. Unlike a (piecewise) linear function in a strictly mathematical sense of the term, piecewise linearity in this document is interpreted such that the value of the slope can be any real number, in particular even zero. In this sense it can be provided that the function defining the course of the braking profile is constant within a segment of the braking time, where the said slope—in correspondence with the above—would be zero in said segment.

In another especially preferred embodiment of the electronic control device according to the invention, it is provided that the value of the braking torque resulting from the course of the braking profile follows a function of the elapsed time since detection of the shutoff signal that monotonically increases from the time of the detection of the shutoff signal to the time of the complete stop of the crankshaft.

Since the value of the braking torque in this embodiment of the control device follows a function of the elapsed time since detection of the shutoff signal that increases monotonically (increases or remains the same), preferably increases strictly monotonically (always increases) from the time of the detection of the shutoff signal to the time of the complete stop of the crankshaft, it is ensured that the braking effect to which the crankshaft is subjected immediately after detection of the shutoff signal increases or at least does not become less during the entire stopping process. In this way a rapid and energy-efficient stopping of the crankshaft—initially independent of the relevant instantaneous value of the rotary speed and its specific course during the overall braking time—is ensured.

A problem of this invention is also solved by a refrigerant compressor for use in a refrigeration unit, preferably in a refrigerator or freezer, where the refrigerant compressor comprises an electronic control device according to the invention.

Thus, all the above described advantages of the electronic control device according to the invention can be utilized in combination with a refrigerant compressor that is suitable for use in a refrigeration unit. In particular, it becomes possible to keep noise generation arising during the stopping process as low as possible and to guarantee a rapid and energy-efficient stopping of the compressor in reaction to the detection of the shutoff signal directed to the refrigerant compressor from a control device of the refrigeration unit.

A problem of this invention is also solved, by a refrigeration unit, preferably a refrigerator or freezer, with a refrigerant compressor having an electronic control device according to the invention. Through this, all the advantages discussed above can also be used in the refrigeration unit according to the invention.

A problem of the invention is solved in the case of a method for operating a refrigerant compressor suitable for use in a refrigeration unit, preferably in a refrigerator or freezer, which comprises a compression mechanism for compression of refrigerant and a drive unit, where the compression mechanism is driven by means of a drive shaft of the drive unit to which a torque is applied, in that the method comprises the following steps:

-   -   detection of a shutoff signal ending an operating phase in which         the refrigerant compressor is operated as designed with a         positive operating torque;     -   detection of a physical process parameter, preferably a rotary         speed of the crankshaft or a power consumption of the         refrigerant compressor;     -   application of a braking torque to the crankshaft immediately         after the detection of the shutoff signal, where the braking         torque opposes the positive operating torque in its direction of         action and the value of the braking torque is a function of the         detected physical process parameter, preferably the rotary speed         of the crankshaft or the power consumption of the refrigerant         compressor.

The method according to the invention enables the braking process to begin immediately after the detection of the shutoff signal and thus at the same time as the stopping process. In addition, it makes it possible to match the braking operation, thus in particular the value of the braking torque applied immediately after detection of the shutoff signal, thus the value of a torque directed against the operating torque, to the operating phase that was ended by the shutoff signal. In this way the crankshaft stopping process overall becomes clearly shorter, through which both the noise generation and the energy consumption connected with the braking torque that causes the crankshaft to stop during the stopping process can be reduced.

In a preferred embodiment of the method according to the invention, it is provided that the physical process parameter is the rotary speed of the crankshaft.

Since the rotary speed that the crankshaft has at the beginning of the stopping process, thus immediately after the detection of the shutoff signal, is important for the braking torque needed to stop the crankshaft, this embodiment enables an specially efficient and rapid stopping of the crankshaft.

Since the braking torque necessary for a set reduction of the rotary speed in a set time interval is much higher in the case of a high rotary speed of the crankshaft than the braking torque that is needed for the same reduction of the rotary speed in the same time interval in the case of a low rotary speed of the crankshaft, in an especially preferred embodiment of the method according to the invention it is provided that the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is essentially inversely proportional to the rotary speed of the crankshaft that it has at the moment of detection of the shutoff signal.

Through this the stopping process can be shortened and the total energy consumption needed to stop the crankshaft can be considerably reduced.

In order to shorten the stopping process further, in another preferred embodiment of the method according to the invention it is provided that the braking torque is maintained at least in a segment within a braking time period, but preferably up to complete stopping of the crankshaft, where the braking time period is the time period between the detection of the shutoff signal and the complete stopping of the crankshaft.

In another especially preferred embodiment of the method according to the invention, it is provided that the braking torque is applied to the crankshaft in the form of a braking profile, where a function defining the course of the braking profile is stored by the electronic control device, and preferably comprises a linear dependency on the current rotary speed of the crankshaft and/or the elapsed time since detection of the shutoff signal.

Through the use of such a braking profile, the braking torque needed to stop the crankshaft can be varied over the entire braking process, which can be utilized for an additional shortening of the stopping process.

Especially preferably, it is provided that the value of the braking torque resulting from the course of the braking profile monotonically increases from the time of the detection of the shutoff signal to the time of complete stopping of the crankshaft.

Thus, it is ensured that the braking effect to which the crankshaft is subjected increases steadily in the course of the stopping process and a rapid stopping of the crankshaft becomes possible.

In order to establish the rotary speed regime, of a plurality of rotary speed regimes set by the specific choice of the preset rotary speed values, in which the crankshaft is running during the braking time each time, in a preferred embodiment of the method according to the invention it is provided that during the braking time the rotary speed of the crankshaft is compared with preset rotary speed values, preferably a number of times, especially preferably continuously, and the braking time is divided at least in segments, preferably the entire braking time, into process time segments, where in each of said process time segments the rotary speed of the crankshaft always lies in a value range that is associated with one of the preset rotary speed values.

In order to obtain an especially easily implemented and efficient braking profile, in another especially preferred embodiment of the method according to the invention it is provided that the course of the braking profile essentially follows a piecewise linear function of the process time, where said function has a segment with a constant slope in each process time segment.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail by means of an embodiment example. The drawing is given as an example and is intended only to represent the ideas of the invention, but not to limit it any way or even to reproduce it conclusively.

Here:

FIG. 1 shows two mutually corresponding diagrams, which represent a stopping process regulated by means of a control device according to the invention.

WAYS TO IMPLEMENT THE INVENTION

FIG. 1 shows two mutually corresponding diagrams, which represent the rotary speed n of a crankshaft of a refrigerant compressor and the torque M applied to the crankshaft during an operating phase II, in which the refrigerant compressor is operated as designed, and also during a stopping process III in the said operating phase, in each case as a function of the process time t.

At time t₀, which coincides with the origin of the abscissa, an electronic control device according to the invention detects a start signal directed to the refrigerant compressor. In reaction to the start signal a drive unit of the refrigerant compressor sets the crankshaft of the refrigerant compressor into motion. After the crankshaft has been initially put into a preset position in the course of a corresponding starting operation I of the refrigerant compressor, the crankshaft is accelerated from said position to a preset rotary speed n_(Start). As soon as the rotary speed of the crankshaft has reached the value n_(Start), the starting operation I is over, and the refrigerant compressor is ready for use in order to make available on demand cooling output needed by a refrigeration unit in which the refrigerant compressor is used. As long as such a demand does nor exist or has not been communicated to the electronic control device according to the invention of the refrigerant compressor from another control device of the refrigeration unit in which the refrigerant compressor is used, the crankshaft maintains the rotary speed n_(Start). Reaching and holding the stalling speed n_(Start) can be managed according to the invention by means of an open control circuit.

As soon as a specific demand for cooling output has been communicated to the electronic control device according to the invention, which cooling output can be automatically set by the other control electronics of the refrigeration unit or can be manually set by a user of the refrigeration unit and which cooling output corresponds to a specific desired temperature in the refrigeration unit, the rotary speed n of the crankshaft is regulated by means of a closed control circuit from the starting speed n_(Start) to a rotary speed set point n_(Soll) in a range between about 700 revolutions per minute (hereinafter abbreviated as “rpm”) and 4000 rpm, which corresponds to the preset demand for cooling output. For this, a specific positive drive torque M is applied to the crankshaft, which is varied in correspondence with a measured value of the current rotary speed n of the crankshaft until the rotary speed set point n_(Soll) is reached. Said rotary speed set point n_(Soll) will be maintained until the required cooling output has been made available to the refrigeration unit and as a result the desired temperature has been reached in the refrigeration unit or a region of the refrigeration unit, for example the freezer compartment of a refrigerator.

After the desired temperature has been reached, this is communicated to the electronic control device in the form of a shutoff signal directed to the refrigerant compressor. The stopping process III that is initiated following the detection of said shutoff signal, at the end of which the crankshaft is at a complete stop, develops according to the invention as follows:

Immediately after detection of the shutoff signal, the electronic control device applies a torque directed opposite to the torque present in the operating phase II (according to its direction) to the crankshaft and thus initiates the braking process at the same time. The stopping process III thus does not have any of the time preceding the braking process that is known from the prior art, in which the crankshaft runs uncontrolled in order to reduce the rotary speed of the crankshaft below a specific sufficiently low value before applying the braking torque. This significantly shortens the stopping process overall, which shortens the time in which the refrigerant compressor runs through a rotary speed range that is critical for noise generation, thus the range between about 700 rpm and 0 rpm.

Since, however, the braking torque that would be necessary to completely stop a crankshaft having a high rotary speed n_(Soll) at the time of the detection of the shutoff signal, thus to bring it to a stop, would be much too high, both from the standpoint of energy efficiency and for reasons of noise technology, and moreover there would also be the danger that components of the control device and or the refrigerant compressor would suffer damage during this harsh braking, it is provided according to the invention that the braking torque applied to the crankshaft immediately after the detection of the shutoff signal is a function of the rotary speed that the crankshaft has at the time of the detection of the shutoff signal.

Specifically, it is provided and is clearly evident from FIG. 1 that the braking torque applied to the crankshaft immediately after the detection of the shutoff signal is lower in the case of a high setpoint value of the rotary speed n_(Soll) of the crankshaft at the time of the detection of the shutoff signal than in the case of a low setpoint value of the rotary speed n_(Soll) of the crankshaft at the time of the detection of the shutoff signal. The value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is thus inversely proportional to the rotary speed n_(Soll) that the crankshaft has at the time of the detection of the shutoff signal. Alternatively, it can also be provided that in establishing the value of the braking torque immediately after the detection of the shutoff signal, a different detected physical process parameter, for example the power consumption of the refrigerant compressor, is used in place of the rotary speed of the crankshaft—the braking torque thus is a function of a different process parameter.

Thus, if the crankshaft at the time of the detection of the shutoff signal has a high rotary speed n_(Soll), the braking torque applied at the beginning of the stopping process will initially lead to a comparably weak braking of the crankshaft, whereas the braking effect is comparably high when the crankshaft has a low rotary speed n_(Soll) at the time of the detection of the shutoff signal.

Because of the braking process that has already been initiated at the same time as the beginning of the stopping process, the rotary speed of the crankshaft decreases faster than in refrigerant compressors according to the prior art, in which the crankshaft initially runs uncontrolled for purposes of reducing the speed before the braking torque is applied to the crankshaft, which is ultimately intended to cause the complete stopping of the crankshaft and to prevent a reversal of the direction of rotation in the last moment of the stopping process.

In order to achieve a continuously greater braking effect with progressive process time t since the detection of the shutoff signal, the braking torque applied to the crankshaft forms a braking profile extending over an entire braking period extending between the detection of the shutoff signal and the complete stopping of the crankshaft. This means that the crankshaft is subjected to a braking torque during the entire braking time. The value of said braking torque, which arises from the course of the braking profile, increases monotonically from the time of the detection of the shutoff signal up to complete stopping of the crankshaft. The course of the braking profile can itself in turn involve a function of the current rotary speed of the crankshaft in each case and/or the process time t (for example, the time that has elapsed since the beginning of the stopping process), where a function defining said course is stored by the control device according to the invention.

In the embodiment examples shown the braking time is—without a loss of generality—divided into four (scenario 1) or into two (scenario 2) process time segments (T₁, T₂, T₃, T₄, or T₁₁, T₂₂). Within each one of these process segments the relevant rotary speed of the crankshaft, which is monitored by the electronic control device at a high frequency, for example at a frequency higher than 10 Hz, and is compared with preset values (n₁, n₂, n₃, n₀, or n₃, n₀) of the rotary speed, in each case lies in a region which is associated in each case with a preset value of the rotary speed. The braking profile, which extends over the entire braking time and thus over all of the process time segments (T₁, T₂, T₃, T₄, or T₁₁, T₂₂), can thus be formed so that it follows the course of a piecewise linear function of the process time t, where the slope of said function has a different constant value in each individual process segment (T₁, T₂, T₃, T₄, or T₁₁, T₂₂).

Below the last non-vanishing, preset value of the rotary speed (in both scenarios this is the rotary speed n₃) the said slope of the said piecewise linear function of the process time t takes the value zero—the braking profile applied to the crankshaft, more precisely its value, is therefore constant in the last process time segment (T₄ in scenario 1, T₂₂ in scenario 2) of the braking time. Thus, the braking behavior produced by the electronic control device according to the invention during the final process time segment, which immediately precedes the complete stopping of the crankshaft, differs from that of the other process time segments, in which the value of the braking torque each time grows, or increases, monotonically.

REFERENCE NUMBER LIST

M torque

n rotary speed of crankshaft

n_(α), n_(β), . . . preset rotary speed values

n_(Start) preset rotary speed

n_(Soll) set value of rotary speed

t process time

t₀ time point of the detection of a start signal

T_(i), T_(ii) process time segments of the braking time (i=1, 2, . . . , 11, 22, . . . ) 

What is claimed is:
 1. An electronic control device for a refrigerant compressor, which comprises at least a drive unit and a compression mechanism that is in operative connection with the drive unit and that has at least one piston that moves back-and-forth in a cylinder of a cylinder block of the refrigerant compressor in an operating state of the refrigerant compressor for compression of refrigerant as designed and is driven via a crankshaft of the drive unit where the electronic control device of the refrigerant compressor is configured at least to detect at least one physical process parameter of the refrigerant compressor, to detect a shutoff signal directed to the refrigerant compressor, which shutoff signal ends an operating phase of the refrigerant compressor, in which operating phase the refrigerant compressor is operated as designed with a positive operating torque, and to control a torque applied by the drive unit to the crankshaft in order to set its rotary speed (n), wherein the electronic control device is further configured to apply a braking torque to the crankshaft immediately after detection of the shutoff signal, where the braking torque is directed opposite to the positive torque that existed during the operating phase and the value of said braking torque is a function of the detected physical process parameter of the refrigerant compressor.
 2. The electronic control device as in claim 1, wherein the physical process parameter is the rotary speed (n) of the crankshaft.
 3. The electronic control device as in claim 1, wherein the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is inversely proportional to the rotary speed (n) of the crankshaft that the crankshaft has at the moment of the detection of the shutoff signal.
 4. The electronic control device as in claim 1, where the braking torque is maintained up to a complete stop of the crankshaft.
 5. The electronic control device as in claim 1, wherein the braking torque applied to the crankshaft is realized as a braking profile, where a function defining the course of the braking profile is stored by the electronic control device.
 6. The electronic control device as in claim 1, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft with preset rotary speed values (n_(α), n_(β), . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.
 7. The electronic control device as in claim 6, wherein the course of the braking profile essentially follows a piecewise linear function, where a segment of the braking time is associated with each of the preset rotary speed values (n_(α), n_(β), . . . ), within which segment said piecewise linear function exhibits an essentially constant slope.
 8. The electronic control device as in claim 5, wherein the value of the braking torque resulting from the course of the braking profile increases monotonously from the time of the detection of the shutoff signal to the time of the complete stop of the crankshaft.
 9. A refrigerant compressor for use in a refrigeration unit where the refrigerant compressor comprises an electronic control device as in claim
 1. 10. A refrigeration unit with a refrigerant compressor as in claim
 9. 11. A method for operating a refrigerant compressor suitable for use in a refrigeration unit, which comprises a compression mechanism for compression of refrigerant and a drive unit, where the compression mechanism is driven by means of a crankshaft of the drive unit that is supplied with a torque, wherein the method comprises the following steps: detection of a shutoff signal ending an operating phase in which the refrigerant compressor is operated as designed with a positive operating torque; detection of a physical process parameter of the refrigerant compressor; a application of a braking torque to the crankshaft immediately after the detection of the shutoff signal, where the braking torque opposes the positive operating torque in its direction of action and the value of the braking torque is a function of the detected physical process parameter of the refrigerant compressor.
 12. The method as in claim 11, wherein the physical process parameter is the rotary speed (n) of the crankshaft.
 13. The method as in claim 11, wherein the value of the braking torque applied to the crankshaft immediately after detection of the shutoff signal is essentially inversely proportional to the rotary speed (n) of the crankshaft that the crankshaft has at the moment of the detection of the shutoff signal.
 14. The method as in claim 11, wherein the braking torque is maintained at least in a segment within a braking time, where the braking time is the time between the detection of the shutoff signal and the complete stop of the crankshaft.
 15. The method as in claim 14, wherein the braking torque is applied to the crankshaft in the form of a braking profile, where a function defining the course of the braking profile is stored by the electronic control device.
 16. The method as in claim 15, wherein the value of the braking torque resulting from the course of the braking profile increases monotonously from the tune of the detection of the shutoff signal to the time of the complete stop of the crankshaft.
 17. The method as in claim 14, wherein during the braking time the rotary speed (n) of the crankshaft is compared with preset rotary speed values (n_(α), n_(β), . . . ) and the braking time is divided at least partially, into process time segments (T_(α), T_(β), . . . ), where in each of said process time segments (T_(α), T_(β), . . . ) the rotary speed (n) of the crankshaft lies in a value range with which one of the preset speed values (n_(α), n_(β), . . . ) is associated.
 18. The method as in claim 17, wherein the course of the braking profile essentially follows a piecewise linear function of the process time, where said function exhibits a segment with constant slope in each process time segment (T_(α), T_(β), . . . ).
 19. The electronic control device of claim 1 wherein the at least one physical process parameter comprises one or more of: rotary speed (n) of the crankshaft, and power consumption of the refrigerant compressor.
 20. The electronic control device as in claim 5, wherein the function defining the course of the braking profile comprises a linear dependency on the current rotary speed (n) of the crankshaft and/or the time elapsed since detection of the shutoff sign.
 21. The electronic control device of claim 6, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft a number of times with preset rotary speed values (n_(α), n_(β), . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.
 22. The electronic control device as in claim 21, wherein the electronic control device is configured to compare the rotary speed (n) of the crankshaft continuously with preset rotary speed values (n_(α), n_(β), . . . ) in a braking time extending between the detection of the shutoff signal and the complete stop of the crankshaft.
 23. The refrigerant compressor as in claim 9, wherein the refrigeration unit comprises a refrigerator or freezer.
 24. The method as in claim 11, wherein the physical process parameter comprises one or more of: rotary speed of the crankshaft, and power consumption.
 25. The method as in claim 14, wherein the braking torque is maintained up to the complete stop of the crankshaft.
 26. The method as in claim 15, wherein the function defining the course of the braking profile comprises a linear dependency on the current rotary speed (n) of the crankshaft and/or of the elapsed time since detection of the shutoff signal.
 27. The method as in claim 17, wherein the rotary speed (n) of the crankshaft is compared a number of times with the preset rotary speed values (n_(α), n_(β), . . . ).
 28. The method as in claim 26, wherein the number of times is continuously with the preset rotary speed values (n_(α), n_(β), . . . ).
 29. The method as in claim 17, wherein the entire braking time is divided into process time segments (T_(α), T_(β), . . . ). 